JP6756843B2 - Manufacturing method of composite substrate - Google Patents

Description

The present invention relates to a composite substrate including a piezoelectric layer made of lithium tantalate and the like and a support substrate, and a method for manufacturing the composite substrate.

A surface acoustic wave (SAW) device in which a surface acoustic wave (IDT) for exciting a surface acoustic wave is formed on a piezoelectric substrate is used as a component for frequency adjustment / selection in a mobile phone or the like.

Piezoelectric materials such as lithium tantalate (LiTaO ₃ ; LT) and lithium niobate (LiNbO ₃ ; LN) are required for surface acoustic wave devices that are small in size, have small insertion loss, and do not allow unwanted waves to pass through. ing.

On the other hand, in the communication standards of mobile phones of the 4th generation and later, the frequency band interval in transmission and reception is narrow and the bandwidth is wide. Under such communication standards, the piezoelectric material used for surface acoustic wave devices needs to sufficiently reduce the characteristic fluctuation due to its temperature. In addition, the shoulder characteristics of the filter and duplexer need to be extremely steep so that extra noise does not protrude between the bands, and a high Q value is required.

As a material used for such a surface acoustic wave device, a composite substrate made of a piezoelectric material and another material has been studied. For example, Patent Document 1 describes on a support substrate a high sound velocity film propagating from an elastic wave sound velocity propagating in a piezoelectric film and a bulk wave sound velocity propagating from a bulk wave sound velocity propagating through a piezoelectric film. A composite substrate in which a low-speed bass sound film and a piezoelectric film are laminated in this order is disclosed, and it has been shown that an elastic wave device using this composite substrate can increase the Q value.

Further, Patent Document 1 discloses that a piezoelectric film is formed by ion implantation as a method for producing this composite substrate.

Further, Non-Patent Document 1 discloses a method in which a lithium tantalate substrate in which H ⁺ ions are injected is bonded to a support substrate via a SiN film or a SiO ₂ film, and then the lithium tantalate substrate is separated into two. ing.

International Publication WO2012 / 086639

H. Kando, et al. , "IMPROVEMENT IN TEMPERATURE CHARACTERISTICS OF PLATE WAVE RESONATOR USING ROTATED Y-CUT LiTaO3 / SIN STRUCTURE", Micro Electro Electro Mechanisms System, Micro Electro Machine

In the method for manufacturing a composite substrate with ion implantation, a composite substrate having a thin piezoelectric film and excellent film thickness uniformity can be obtained, while the present inventors have a method for manufacturing a composite substrate with ion implantation. As a result of detailed examination of, it was found that there are some problems.

That is, when ions are implanted into a LiTaO ₃ substrate as used in Patent Document 1 and Non-Patent Document 1 and these are separated, the injected H ^{+ and} other ions cause Li ions in the LiTaO ₃ substrate. It was clarified that the amount of Li varied in the formed LiTaO ₃ layer because a part of the Li was ejected. Such a variation in the amount of Li becomes apparent as a variation in characteristics such as the sound velocity of the surface acoustic wave and the electromechanical coupling coefficient, which poses a big problem in the manufacture of the surface acoustic wave device.

Further, in this case, since the amount of Li in the LiTaO ₃ layer is reduced, the performance of LiTaO _{3 as} a piezoelectric material is lowered. For example, when a composite substrate is produced by using a LiTaO ₃ substrate having a congruent composition (Li / Li + Ta = 48.5 mol%) as a piezoelectric substrate and ion implantation is performed, the amount of Li is reduced to 48.5 mol. It will be less than%.
Further, even if a LiTaO ₃ substrate having a constant ratio (stoichiometry) composition (Li / Li + Ta = 49.95 to 50.0 mol%) prepared by a double crucible method or the like is used as the piezoelectric substrate, the amount of Li is at least 0. It decreases by about 1% to 49.9 mol% or less.

Therefore, conventionally, it has not been possible to obtain a composite substrate having _three layers of LiTaO having a stoichiometric composition, having a thin film thickness that cannot be obtained by a manufacturing method by polishing and grinding, and having excellent film thickness uniformity.

Therefore, an object of the present invention is to provide a composite substrate and a method for manufacturing a composite substrate, which are composed of a piezoelectric layer and a support substrate having a small variation in the amount of Li.

As a result of diligent studies to achieve the above object, the present inventors have found that the variation in the amount of Li in the piezoelectric layer can be suppressed by applying Li diffusion to the piezoelectric layer, and have reached the present invention. It is a thing.

That is, the present invention is a method for manufacturing a composite substrate including a piezoelectric layer and a support substrate, in which a step of injecting ions into the piezoelectric substrate and a step of joining the piezoelectric substrate and the support substrate. After the step of joining the piezoelectric substrate and the support substrate, the step of separating the piezoelectric layer bonded to the support substrate and the remaining piezoelectric substrate at the ion injection portion of the piezoelectric substrate is separated. It is characterized by including a step of diffusing Li into the piezoelectric layer after the step.

Further, in the present invention, after the step of joining the piezoelectric substrate and the support substrate, the step of raising the temperature of the piezoelectric substrate to the Curie temperature or higher and lowering the temperature to the Curie temperature or lower in a state where an electric field is applied may be included. Preferably, after the step of joining the piezoelectric substrate and the support substrate, a step of raising the temperature of the piezoelectric substrate to restore the piezoelectricity can also be included.

In the present invention, the step of joining the piezoelectric substrate and the support substrate is preferably performed by a surface-activated room temperature bonding method, and an intervening layer can be provided between the piezoelectric layer and the support substrate.

In the step of diffusing Li into the piezoelectric layer of the present invention, it is preferable that the piezoelectric layer has a pseudo-stoikiometry composition, and the ion species in the step of implanting ions into the piezoelectric substrate are hydrogen ions and hydrogen molecules. It is preferably at least one type of ion selected from an ion and a helium ion.

The piezoelectric substrate of the present invention preferably has a range in which the Li concentration differs in the thickness direction thereof, and is preferably lithium tantalate or lithium niobate. Further, the support substrate preferably contains at least one material selected from silicon, sapphire, silicon carbide, and spinel.

The present invention is a method for manufacturing a composite substrate including a piezoelectric layer and a support substrate, which comprises a step of injecting ions into the piezoelectric substrate and a step of joining the piezoelectric substrate and the support substrate. After the step of joining the piezoelectric substrate and the support substrate, the ion injection portion of the piezoelectric substrate includes a step of separating the piezoelectric layer bonded to the support substrate and the remaining piezoelectric substrate. The substrate is lithium tantalate, and has a portion having a Li concentration of 48.5 ± 0.5% and a portion having a Li concentration of 50.0 ± 0.5%, and the substrate surface in the thickness direction thereof. It is characterized in that the side has a range in which the Li concentration is higher.

The present invention is a method for manufacturing a composite substrate including a piezoelectric layer and a support substrate, which comprises a step of injecting ions into the piezoelectric substrate and a step of joining the piezoelectric substrate and the support substrate. After the step of joining the piezoelectric substrate and the support substrate, the ion injection portion of the piezoelectric substrate includes a step of separating the piezoelectric layer bonded to the support substrate and the remaining piezoelectric substrate. The substrate is lithium tantalate or lithium niobate, and the Li concentration at the ion-injected depth position of the piezoelectric substrate is more than 50.0%.

The present invention is a method for manufacturing a composite substrate including a piezoelectric layer and a support substrate, which comprises a step of injecting ions into the piezoelectric substrate and a step of joining the piezoelectric substrate and the support substrate. After the step of joining the piezoelectric substrate and the support substrate, the ion injection portion of the piezoelectric substrate includes a step of separating the piezoelectric layer bonded to the support substrate and the remaining piezoelectric substrate. The substrate is lithium tantalate, and has a portion having a Li concentration of 48.5 ± 0.5% and a portion having a Li concentration of 50.0 ± 0.5%, and the substrate surface in the thickness direction thereof. The side has a range in which the Li concentration is higher, and the Li concentration at the depth position where ions are injected from the piezoelectric substrate is more than 50.0%.

In the present invention, the Li concentration from the surface of the piezoelectric substrate on the side to be bonded to the support substrate to the depth position where ions are implanted is preferably 49.0% or more and 52.5% or less. Further, it is preferable to provide an intervening layer between the piezoelectric layer and the support substrate.

The present invention is a composite substrate including a piezoelectric layer and a support substrate. The piezoelectric layer is lithium tantalate or lithium niobate, and the Li concentration on the surface of the piezoelectric layer is 49.9. %, The thickness of the piezoelectric layer is 1.0 μm or less, and the maximum height Rz value of the surface roughness of the piezoelectric layer is 10% or less of the thickness of the piezoelectric layer. It is a thing.

In the present invention, it is preferable that an intervening layer is present between the piezoelectric layer and the support substrate.

According to the present invention, it is possible to manufacture a composite substrate having a small variation in the amount of Li in the piezoelectric layer. Further, by using the composite substrate manufactured by the present invention, it is possible to stably manufacture a surface acoustic wave device having excellent characteristics.
Further, according to the present invention, it is possible to manufacture a composite substrate having _three LiTaO layers having a stoichiometric composition, having a thin piezoelectric layer, and having excellent film thickness uniformity.

It is an input impedance waveform of a SAW resonator using the composite substrate of Example 1. It is a graph which showed the Q value of the SAW resonator using the composite substrate of Example 1. It is a graph which showed the profile in the depth direction of the Li amount of the LT substrate of Example 3. It is a figure which shows an example of the production flow of the composite substrate of this application. It is a graph which showed the profile in the depth direction of the Li amount of the LT substrate of Example 5.

The present invention is a method for manufacturing a composite substrate including a piezoelectric layer and a support substrate. Here, the material used for the piezoelectric layer and the support substrate is not particularly limited, but as the piezoelectric material, lithium tantalate or lithium niobate containing Li in the composition is preferable, and these single crystals can be used. When the piezoelectric material is a lithium tantalate single crystal, the crystal orientation is preferably a rotation of 36 ° to 49 ° Y-cut.

Further, the support substrate material can be selected from silicon, sapphire, silicon carbide, spinel and the like, and a laminated substrate containing these can be used.

The present invention includes a step of implanting ions into a piezoelectric substrate. In this step, ions are implanted into an arbitrary depth of the piezoelectric substrate, and in the subsequent separation step of the piezoelectric substrate, the ions are separated at the ion implantation portion. Therefore, the depth of ion implantation in this step determines the thickness of the piezoelectric layer after the piezoelectric substrate is separated. Therefore, it is preferable that the depth of ion implantation is equal to the thickness of the piezoelectric layer of the target composite substrate, or slightly increased in consideration of the polishing allowance and the like. The depth of ion implantation varies depending on the material, ion species, etc., but can be adjusted by the accelerating voltage of the ions.

The ion species used in the ion implantation step is not particularly limited as long as it disturbs the crystallinity of the piezoelectric substrate material, but is preferably a light element such as hydrogen ion, hydrogen molecule ion, or helium ion. By using these ion species, ions can be implanted with a small accelerating voltage, and there are advantages such as less restrictions on the device, less damage to the piezoelectric substrate, and better distribution in the depth direction.

Here, when the ion species used in the ion implantation step is hydrogen ion, the dose amount is preferably 1 × 10 ¹⁶ to 1 × 10 ¹⁸ atm / cm ² , and the ion species is hydrogen molecule ion. The dose amount is preferably 1 × 10 ¹⁶ to 2 × 10 ¹⁸ atm / cm ² . When the ion species is helium ion, the dose amount is preferably 2 × 10 ¹⁶ to 2 × 10 ¹⁸ atm / cm ² .

The present invention also includes a step of joining the piezoelectric substrate and the support substrate. The joining method in this step is not particularly limited, and may be joined via an adhesive or the like, or a direct joining method such as a diffusion joining method, a room temperature joining method, a plasma activated joining method, or a surface activated room temperature joining method is also available. Can be used. At this time, an intervening layer may be provided between the piezoelectric substrate and the support substrate.
There is a large difference in the coefficient of thermal expansion between the piezoelectric substrate such as lithium tantalate single crystal substrate or lithium niobate single crystal substrate and the support substrate such as silicon or sapphire, and the room temperature bonding method is used to suppress peeling and defects. However, the room temperature joining method also has an aspect that the joining system is limited. In addition, heat treatment may be required to restore the crystallinity of the piezoelectric layer.

The surface activation treatment method in the surface activation bonding method is not particularly limited, but ozone water treatment, UV ozone treatment, ion beam treatment, plasma treatment and the like can be used.

In the present invention, after joining the piezoelectric substrate and the support substrate, the piezoelectric layer bonded to the support substrate and the remaining piezoelectric substrate are separated at the ion implantation portion of the piezoelectric substrate described above. At this time, the separation method is not particularly limited, but the separation can be performed by, for example, heating to a temperature of 200 ° C. or lower and applying a mechanical stress such as a wedge to one end of the ion-implanted portion.

The surface roughness and thickness of the piezoelectric layer bonded to the support substrate can be adjusted by polishing the surface thereof. The surface roughness and thickness of the piezoelectric layer may be arbitrarily set as needed, but the surface roughness is preferably 0.4 nm or less in terms of RMS value, and the thickness is preferably about 0.5 to 5 μm. Further, the remaining piezoelectric substrate can be re-polished and reused as the piezoelectric substrate.

In the method for producing a composite substrate with ion implantation, the thickness of the piezoelectric layer can be controlled to 1.0 μm or less, and the surface roughness can be controlled to 10% or less of the thickness at the maximum height Rz value. Preferably, the thickness is controlled to 0.8 μm or less, and the surface roughness is controlled to 5% or less of the thickness at the maximum height Rz value. Controlling the film thickness and uniformity at this level is difficult with the method of polishing and grinding the bonded piezoelectric substrate.

Further, the present invention includes a step of diffusing Li into the piezoelectric layer bonded to the support substrate after the separation step. By this step, the Li deficiency of the piezoelectric layer generated in the ion implantation step can be compensated. The method for diffusing Li into the piezoelectric layer is not particularly limited, and Li can be diffused by bringing the Li diffusion source into contact with the piezoelectric layer. At this time, the state of the Li diffusion source may be solid, liquid, or gas.

As a specific method of this Li diffusion step, when the piezoelectric material is LiTaO ₃ , a composition containing the constituent elements Li, Ta, O is used. For example, Li can be diffused in the piezoelectric layer by embedding the piezoelectric layer bonded to the support substrate in a powder containing Li ₃ TaO ₄ as a main component and heating the mixture. Li can also be diffused into the piezoelectric layer by impregnating the piezoelectric layer bonded to the support substrate into a melt in which LiNO ₃ , NaNO ₃ , and KNO ₃ are mixed at an equimolar ratio.

In this Li diffusion step, it is preferable to perform Li diffusion so that the piezoelectric layer has a pseudo-stoikiometry composition. In this way, the characteristics such as the electromechanical coupling coefficient, the temperature characteristic, and the Q value can be improved as compared with the case where the piezoelectric layer has a normal congruent composition.

Here, the pseudo-stoikiometry composition is determined based on common general knowledge depending on the piezoelectric material, but when the piezoelectric material is LiTaO ₃ , the ratio of Li to Ta is Li: Ta = 50-α: 50 + α. It means that α is in the range of −1.0 <α <2.5. Further, when the piezoelectric material is LiNbO ₃ , the ratio of Li to Nb is Li: Nb = 50-α: 50 + α, and α is in the range of −1.0 <α <2.5.

The Li concentration of the lithium tantalate single crystal substrate and the lithium niobate single crystal substrate may be measured by a known method, and can be evaluated by, for example, Raman spectroscopy. It is known that for a lithium tantalate single crystal substrate, there is a substantially linear relationship between the half width of the Raman shift peak and the Li concentration (Li / (Li + Ta) value). Therefore, it is possible to evaluate the composition of the oxide single crystal substrate at an arbitrary position by using an equation expressing such a relationship.

The relational expression between the half width of the Raman shift peak and the Li concentration can be obtained by measuring the Raman half width of several samples whose composition is known and whose Li concentration is different, but the conditions for Raman measurement are the same. If so, a relational expression already clarified in the literature or the like may be used.

For example, for a lithium tantalate single crystal, the following formula 1 may be used (see 2012 IEEE International Ultrasonics Symposium Proceedings, Page (s) 1252-1255).

[Number 1]
Li / (Li + Ta) = (53.15-0.5FWHM1) / 100

Here, "FWHM1" is the half width of the Raman shift peak near 600 cm ^-1 . Please refer to the literature for the details of the measurement conditions.

When a lithium tantalate single crystal substrate or a lithium niobate single crystal substrate is used as the piezoelectric substrate, one having a Li concentration that is substantially uniform over the thickness direction can be used, and the Li concentration can be determined by the congluent composition or the congluent composition. It can be a pseudo-stoichiometric composition.

A piezoelectric single crystal substrate having a congluent composition is preferable because it can be relatively easily produced by the Czochralski method or the like. On the other hand, if a piezoelectric single crystal substrate having a pseudo-stoikiometry composition is used, the step of diffusing Li into the piezoelectric layer bonded to the support substrate can be performed in a short time.

A piezoelectric single crystal substrate having a pseudo-stoikiometry composition can be obtained by a known double crucible method, but using this substrate increases the cost. Therefore, as the lithium tantalate single crystal substrate or the lithium niobate single crystal substrate, those having a range in which the Li concentration differs in the thickness direction can be used. That is, when this substrate is joined to a support substrate to form a composite substrate, a piezoelectric substrate having a pseudo-stoikiometry composition at a portion to be a piezoelectric layer can be used.

Such a piezoelectric substrate can be obtained by diffusing Li from the surface of the substrate to the inside of the piezoelectric single crystal substrate having a congluent composition. At this time, by adjusting the reaction time, the reaction temperature, and the like, it is possible to obtain a piezoelectric substrate having a pseudo-stoichiometry composition on the surface and a congluent composition on the inside. Further, it is preferable that the pseudo-stoikiometry composition is at least from the surface of the substrate to a depth equivalent to the thickness of the target piezoelectric layer.

Specifically, when a lithium tantalate substrate is used as the piezoelectric substrate, it has a portion where the Li concentration is 48.5 ± 0.5 mol% and a portion where the Li concentration is 50.0 ± 0.5 mol%. It is preferable that the substrate has a range in which the Li concentration is higher on the surface side of the substrate in the thickness direction thereof.

When a lithium tantalate substrate or a lithium niobate substrate is used as the piezoelectric substrate, the Li concentration at the ion implantation depth position of the piezoelectric substrate is preferably more than 50.0 mol%, and 50.05 mol. % Or more is more preferable, and 50.1 mol% or more is further preferable. In this way, even if the Li concentration is reduced by ion implantation, the Li concentration of the piezoelectric layer can be increased to more than 49.9 mol%, and excellent characteristics can be obtained.
The Li concentration at the ion-implanted depth position of the piezoelectric substrate is preferably 52.5 mol% or less, more preferably 51.0 mol% or less, and preferably 50.5 mol% or less.

Further, the Li concentration from the surface of the piezoelectric substrate on the side to be bonded to the support substrate to the depth position where ions are implanted is preferably 49.0 mol% or more and 52.5 mol% or less. It is more preferably 49.5 mol% or more, further preferably more than 50.0 mol%, and even more preferably 50.1 mol% or more.

The present inventors have found that the Li concentration of the piezoelectric substrate correlates with the decrease in Li concentration due to ion implantation. That is, the amount of decrease in Li concentration when ions are implanted into the piezoelectric substrate having a pseudo-stoichiometry composition is smaller than the amount of decrease in Li concentration when ions are implanted into the piezoelectric substrate having a congluent composition. That is, in the case of the piezoelectric substrate having the congluent composition, a decrease of about 0.4 mol% is observed, but in the case of the piezoelectric substrate having the pseudo-stoichiometry composition, the decrease is about 0.1 mol%, and there is little variation.

Therefore, if the Li concentration from the surface of the piezoelectric substrate to the support substrate to the depth position where the ions are implanted, especially the Li concentration at the depth position where the ions are implanted is set to more than 50.0 mol%, the piezoelectric substrate is piezoelectric. It is not necessary to have a step of diffusing Li into the piezoelectric layer after the step of separating the body substrate.

As will be described later, by implanting ions into the piezoelectric substrate, the piezoelectricity of the portion through which the ions have passed may be impaired. However, in this way, the piezoelectricity is not easily impaired, and the piezoelectricity is high. It exhibits piezoelectricity without recovery treatment.

According to the present invention, by using Li diffusion, the Li concentration on the surface of the piezoelectric layer is more than 49.9 mol%, the thickness of the piezoelectric layer is 1.0 μm or less, and the piezoelectric layer is piezoelectric, which was impossible in the past. A composite substrate having a maximum height Rz value of the surface roughness of the body layer of 10% or less of the thickness of the piezoelectric layer can be produced.

The Li concentration on the surface of the piezoelectric layer is preferably 49.95 mol% or more, and preferably 52.0 mol% or less.
The thickness of the piezoelectric layer is preferably 0.8 μm or less, and more preferably 0.6 μm or less. The maximum height Rz value of the surface roughness of the piezoelectric layer is preferably 5% or less, more preferably 1% or less of the thickness of the piezoelectric layer.
The maximum height Rz is a parameter defined in JIS B 0601: 2013 (ISO 4287: 1997), and can be measured based on these standards.

Further, in the manufacturing method of the present invention, an intervening layer may be provided between the piezoelectric layer of the composite substrate and the support substrate. The material of the intervening layer is not particularly limited, but is preferably an inorganic material, for example, SiO ₂ , SiO _{2 ± 0.5} , Ti-doped SiO ₂ , a-Si, p-Si, a-SiC, Al ₂ O _{3 and the} like may be contained as a main component. Further, the intervening layer may be a laminated layer made of a plurality of materials.

By the way, by implanting ions into the piezoelectric substrate, the piezoelectricity of the portion through which the ions have passed may be impaired. Therefore, after joining the piezoelectric substrate and the support substrate, it is preferable to perform a step of raising the temperature of the piezoelectric substrate to the Curie temperature or higher and lowering the temperature to the Curie temperature or lower in a state where an electric field is applied. By doing so, the piezoelectricity of the piezoelectric layer can be restored. Further, this step may be performed at the same time as the step of diffusing Li in the piezoelectric layer.

In the above step, it may be difficult to apply an electric field depending on the type of the support substrate, and the piezoelectricity can be restored by raising the temperature of the piezoelectric substrate. The temperature at this time is preferably not less than the Curie temperature and is about 500 ° C. to 700 ° C.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to the following Examples.

<Example 1>
In Example 1, first, a 4-inch diameter lithium tantalate (Li: Ta = 48.3: 51.7) single crystal ingot having a congluent composition subjected to a single polarization treatment was sliced, wrapped, and polished. A lithium tantalate substrate having a thickness of 250 μm and a mirror surface on one side and a Y-cut 42 ° rotation was prepared.

Next, as a support substrate, a sapphire substrate having a thickness of 500 μm and a mirror surface on one side was prepared. Then, it was confirmed that the surface roughness on the mirror surface of the LT substrate and the sapphire substrate was 1.0 nm or less in RMS value. Subsequently, hydrogen molecule ions were injected from the mirror surface side of the LT substrate. At this time, the dose amount was 9 × 10 ¹⁶ atm / cm ² , and the accelerating voltage was 160 KeV.

The ion-implanted LT substrate and sapphire substrate are described in "Takagi H. et al," Room-temperature wafer bonding argonbeam activation "From Proceedings-Electrochemical Bond (200). And Applications V), 265-274. ”, The bonding was performed using the room temperature bonding method described in the above.

Specifically, the cleaned LT substrate and sapphire substrate were set in a high vacuum chamber, and the surface of the substrate to be joined was irradiated with a high-speed atomic beam of neutralized argon to perform activation treatment. Then, the LT substrate and the sapphire substrate were bonded by bonding.

Then, the bonded substrate was heated to 110 ° C., and a wedge was driven into one end of the ion-implanted portion of the piezoelectric substrate to separate the piezoelectric layer bonded to the support substrate and the remaining piezoelectric substrate.

The thickness of the piezoelectric layer at this time was 900 nm, but the surface of the piezoelectric layer was polished by 200 nm to make the thickness of the piezoelectric layer 700 nm. Moreover, when the maximum height Rz of the surface roughness was measured using an atomic force microscope (AFM), the value was 1 nm.

A bonded substrate composed of this piezoelectric layer and a sapphire support substrate is induced by applying vertical vibration in the thickness direction to the main surface and the back surface using a piezo d33 / d15 meter (model ZJ-3BN) manufactured by the Institute of Voice, Chinese Academy of Sciences. When the voltage waveform was observed, the piezoelectric response could not be observed on this bonded substrate, and the piezoelectricity could not be confirmed.

Next, the temperature of this bonded substrate was raised to 650 ° C., which is higher than the Curie temperature of lithium tantalate, and the temperature was gradually lowered to room temperature with an electric field of 4000 V / m applied in the approximate + Z direction of the LT substrate. ..

After this polarization treatment, again, using a piezo d33 / d15 meter (model ZJ-3BN) manufactured by the Vocal Research Institute of the Chinese Academy of Sciences, observation of the voltage waveform induced by applying vertical vibration in the thickness direction to the main surface and the back surface was observed. As a result, the piezoelectric response could be observed at all points of this bonded substrate, and the piezoelectricity could be confirmed.

Subsequently, a laser Raman spectrophotometer (LabRam HR series manufactured by HORIBA Scientific Co., Ltd., Ar ion laser, spot size 1 μm, room temperature) was used at several locations on the surface of the piezoelectric layer to measure the amount of Li in the vicinity of 600 cm ^-1. The half-value width (FWHM1) of the Raman shift peak was measured, and the amount of Li was calculated from the measured half-value width using the above equation 1.

As a result, the amount of Li on the surface of the piezoelectric layer varied from 47.9 to 48.2 mol%. The amount of Li was calculated in the same manner for the surface of the LT substrate before ion implantation, but the amount of Li at that time was uniform at 48.3 mol%.
Therefore, in this LT substrate, the amount of Li is reduced by a maximum of 0.4 mol% by ion implantation.

Therefore, the liquid-phase diffusion of Li described in "Apple.Psysic.Let, Vol.62,2468 (1993)" was applied to the bonded substrate having the variation. Specifically, LiNO ₃ , NaNO ₃ , and KNO ₃ were mixed at an equimolar ratio in an alumina container and heated to 300 ° C., and the melt was impregnated with a polarized bonded substrate for 12 hours. ..

After such Li diffusion treatment, the bonded substrate was washed to complete a composite substrate composed of an LT piezoelectric layer and a sapphire support substrate. Subsequently, Raman spectroscopy was performed on the produced composite substrate in the same manner as described above, and the amount of Li on the surface of the piezoelectric layer was calculated. As a result, the amount of Li was 48.3 mol% at all the measurement points and was uniform. ..

Next, a sputtering treatment was performed on the surface of the piezoelectric layer of the composite substrate to form an Al film having a thickness of 0.4 μm. Subsequently, a resist was applied, the electrode pattern of the resonator was exposed and developed using a stepper, and the electrodes of the SAW device were further formed by RIE (Reactive Ion Etching). The wavelength of one resonator here was set to 5 μm.

When the input impedance waveform of the SAW of the resonator produced in this way was confirmed using an RF prober, the results shown in FIG. 1 were obtained. For comparison, FIG. 1 also shows an input impedance waveform of a resonator (Comparative Example 1) using a composite substrate produced in the same manner as in Example 1 except that Li diffusion treatment is not performed.

Further, FIG. 2 shows the Q values of the resonators of Example 1 and Comparative Example 1. The Q value was calculated by the following mathematical formula 2 (see 2010 IEEE International Ultrasonics Symposium Proceedings, Page (s) 861-863).

[Number 2]
Q (f) = ω * τ (f) * | Γ | / (1- | Γ | ² )

Here, ω is the angular frequency, τ (f) is the group delay time, and Γ is the reflectance coefficient measured by the network analyzer.

Further, Table 1 below shows the electromechanical coupling coefficient (K ² ) of the resonator of Example 1, the maximum value of the Q value, and the frequency temperature coefficient of the resonance frequency and the antiresonance frequency in the temperature range of 20 ° C. to 85 ° C. The values of TCF) are shown respectively. Here, the electromechanical coupling coefficient (K ² ) was calculated by the following mathematical formula 3.

[Number 3]
K ² = (πfr / 2fa) / tan (πfr / 2fa)
fr: Resonant frequency fa: Anti-resonant frequency

Further, Table 1 below also shows the values of the resonance load Qso and the anti-resonance load Qpo calculated by the following formula 4 by the MBVD model (John D. et al., "Modified Butterworth-Van Dyke Circuit for FBAR Resonator and Electronics Engineer". See "Measurement System", IEEE ULTRASONICS SYSTEMSIUM, 2000, pp.863-868).

Table 1 below shows the results of a resonator (Comparative Example 2) using a 42 ° Y-cut LT single crystal substrate having a Li content of 48.3 mol% (congluent composition) as compared with Comparative Example 1 for comparison. Is also shown.

<Example 2>
In Example 2, ions were implanted into the LT substrate in the same manner as in Example 1 to bond the LT substrate and the sapphire substrate. Further, the LT substrate was separated in the ion implantation section, and the surface of the piezoelectric layer was polished to obtain a bonded substrate composed of the LT piezoelectric layer and the sapphire support substrate.

Subsequently, this bonded substrate was embedded in a powder containing Li ₃ TaO ₄ as a main component, which was spread in a small container. At this time, as the powder containing Li ₃ TaO ₄ as a main component, a powder obtained by mixing a powder having a molar ratio of Li ₂ CO ₃ : Ta ₂ O ₅ = 7: 3 and firing at 1300 ° C. for 12 hours was used. ..

Then, set the small container into an electric furnace, the furnace as a N ₂ atmosphere and heated at 750 ° C. 100 hours. Subsequently, an electric field of 4000 V / m was applied in the approximate + Z-axis direction of the LT substrate between 750 ° C. and 500 ° C. in the temperature lowering process, and then the temperature was gradually lowered to room temperature.

After this treatment, the surface of the piezoelectric layer was polished by about 10 nm to complete a composite substrate composed of the LT piezoelectric layer and the sapphire support substrate. No cracks or cracks occurred on this composite substrate. Moreover, when the maximum height Rz of the surface roughness was measured using an atomic force microscope (AFM), the value was 1 nm.

Then, with respect to the composite substrate thus produced, the voltage waveform induced by applying vertical vibration in the thickness direction to the main surface and the back surface was observed in the same manner as in Example 1, and all the parts of the bonded substrate were observed. The piezoelectric response could be observed in, and the piezoelectricity could be confirmed.

Further, as a result of performing laser Raman spectroscopic measurement on several points on the surface of the piezoelectric layer and calculating the amount of Li in the same manner as in Example 1, the amount of Li was 50.2 mol% in all the measurement points and was uniform. It was a pseudo-stoikiometry composition.

Further, with respect to the composite substrate of Example 2, electrodes were formed in the same manner as in Example 1 to produce a resonator, and the SAW resonator was evaluated in the same manner as in Example 1 and the results are shown in Table 1 below. ..

<Example 3>
In Example 3, first, a 42 ° rotating Y-cut having a thickness of 300 μm was obtained from a 4-inch diameter lithium tantalate (Li: Ta = 48.3: 51.7) single crystal ingot having a congluent composition subjected to a single polarization treatment. The lithium tantalate substrate was cut out. Next, the surface roughness of the cut out LT substrate was adjusted to 0.15 μm in arithmetic average roughness Ra value by the wrapping step, and the thickness of the LT substrate was set to 250 μm.

Further, both sides of the LT substrate were polished to obtain a quasi-mirror surface having a surface roughness of 0.01 μm in Ra value. Subsequently, this LT substrate was embedded in a powder containing Li ₃ TaO ₄ as a main component, which was spread in a small container. At this time, as the powder containing Li ₃ TaO ₄ as a main component, a powder obtained by mixing a powder having a molar ratio of Li ₂ CO ₃ : Ta ₂ O ₅ = 7: 3 and firing at 1300 ° C. for 12 hours was used. ..

Then, set the small container into an electric furnace, the furnace as a N ₂ atmosphere and heated at 975 ° C. 24 hours to diffuse Li to LT substrate. After this treatment, one side of the LT substrate was mirror-polished.

Then, with respect to the LT substrate subjected to the Li diffusion treatment, the half width (FWHM1) of the Raman shift peak near 600 cm ^-1 was measured from the surface to the depth direction using the same laser Raman spectroscopic measuring device as in Example 1. When the Li amount was calculated from the measured half-value width using the above formula 1, the profile of the Li amount in the depth direction shown in FIG. 3 was obtained.

Next, as a support substrate, a sapphire substrate having a thickness of 500 μm and a mirror surface on one side was prepared. Then, it was confirmed that the surface roughness of the mirror surface of the LT substrate and the sapphire substrate subjected to the Li diffusion treatment was 1.0 nm or less in RMS value.

Subsequently, hydrogen molecule ions were injected from the mirror surface side of the LT substrate. At this time, the dose amount was 9 × 10 ¹⁶ atm / cm ² , and the accelerating voltage was 160 KeV.

Next, the LT substrate and the sapphire substrate that had been ion-implanted were bonded using the surface-activated room temperature bonding method in the same manner as in Example 1. Further, in the same manner as in Example 1, the LT substrate was separated in the ion implantation section, and the surface of the piezoelectric layer was polished to obtain a bonded substrate composed of the LT piezoelectric layer and the sapphire support substrate.

The thickness of the piezoelectric layer at this time was 900 nm, but the surface of the piezoelectric layer was polished by 200 nm to make the thickness of the piezoelectric layer 700 nm.

Further, as a result of performing laser Raman spectroscopic measurement on several points on the surface of the piezoelectric layer and calculating the amount of Li in the same manner as in Example 1, the amount of Li on the surface of the piezoelectric layer was 49.5 to 49.6 mol%. There was variation. The amount of Li was calculated in the same manner for the surface of the LT substrate before ion implantation, but the amount of Li at that time was uniform at 49.7 mol%.
Therefore, in this LT substrate, the amount of Li is reduced by a maximum of 0.2 mol% by ion implantation.

Subsequently, this bonded substrate was embedded in a powder containing Li ₃ TaO ₄ as a main component, which was spread in a small container. At this time, as the powder containing Li ₃ TaO ₄ as a main component, a powder obtained by mixing a powder having a molar ratio of Li ₂ CO ₃ : Ta ₂ O ₅ = 7: 3 and firing at 1300 ° C. for 12 hours was used. ..

Then, set the small container into an electric furnace, the furnace as a N ₂ atmosphere and heated at 750 ° C. 20 hours. Subsequently, an electric field of 4000 V / m was applied in the approximate + Z-axis direction of the LT substrate between 750 ° C. and 500 ° C. in the temperature lowering process, and then the temperature was gradually lowered to room temperature.

After this treatment, the surface of the piezoelectric layer was polished by about 10 nm to complete a composite substrate composed of the LT piezoelectric layer and the sapphire support substrate. No cracks or cracks occurred on this composite substrate. Moreover, when the maximum height Rz of the surface roughness was measured using an atomic force microscope (AFM), the value was 1 nm.

As in Example 1, the composite substrate thus produced was observed to be induced by applying vertical vibration in the thickness direction to the main surface and the back surface. As a result, piezoelectricity was observed at all points of the bonded substrate. The response could be observed and the piezoelectricity could be confirmed.

Further, as a result of performing laser Raman spectroscopic measurement at several points on the surface of the piezoelectric layer and calculating the amount of Li in the same manner as in Example 1, the amount of Li was 50.2 mol% at all the measurement points and was uniform. It was a pseudo-stoikiometry composition.

Further, with respect to the composite substrate of Example 3, electrodes were formed in the same manner as in Example 1, a resonator was produced, and the SAW resonator was evaluated in the same manner as in Example 1. Almost the same result was obtained.

<Example 4>
In Example 4, an LT substrate subjected to Li diffusion treatment was prepared by the same method as in Example 3. The profile of the Li amount in the depth direction of this LT substrate is almost the same as that of Example 3 shown in FIG.

Next, hydrogen molecule ions were injected from the mirror surface side of this LT substrate. At this time, the dose amount was 9 × 10 ¹⁶ atm / cm ² , and the accelerating voltage was 160 KeV.

Subsequently, a SiO ₂ film having a thickness of 5 μm was deposited on the mirror surface side of the LT substrate on which the ions were implanted by using the room temperature CVD method. Further, the LT / SiO ₂ substrate was heated at 350 ° C. for 48 hours to degas, and then the SiO ₂ film was polished to a thickness of 2.7 μm.

Next, as a support substrate, a Si (SiO ₂ / Si) substrate having a mirror surface on one side and an oxidation (SiO ₂ ) film formed on the surface was prepared. The thickness of this support substrate was 400 μm, and the thickness of the oxide film was 0.3 μm.

Further, an a-Si film having a thickness of 50 nm was formed on the mirror surface side of the SiO ₂ / Si substrate by using the room temperature CVD method. Then, it was confirmed that the surface roughness of the LT / SiO ₂ substrate and the a-Si / SiO ₂ / Si substrate on the mirror surface was 1.0 nm or less in RMS value.

Subsequently, these substrates were bonded by a surface-activated room temperature bonding method by plasma activation treatment. Further, in the same manner as in Example 1, the LT substrate was separated in the ion implantation section, and the surface of the piezoelectric layer was polished to obtain a bonded substrate composed of the LT piezoelectric layer and the Si support substrate.

The thickness of the piezoelectric layer at this time was 900 nm, but the surface of the piezoelectric layer was polished by 200 nm to make the thickness of the piezoelectric layer 700 nm. Here, an intervening layer exists between the LT piezoelectric layer and the Si support substrate, and the intervening layer has a laminated structure of SiO ₂ / a-Si / SiO ₂ .

Further, as a result of performing laser Raman spectroscopic measurement on several points on the surface of the piezoelectric layer and calculating the amount of Li in the same manner as in Example 1, the amount of Li on the surface of the piezoelectric layer was 49.5 to 49.6 mol%. There was variation. The amount of Li was calculated in the same manner for the surface of the LT substrate before ion implantation, but the amount of Li at that time was uniform at 49.7 mol%.
Therefore, in this LT substrate, the amount of Li is reduced by a maximum of 0.2 mol% by ion implantation.

Next, this bonded substrate was embedded in a powder containing Li ₃ TaO ₄ as a main component, which was spread in a small container. At this time, as the powder containing Li ₃ TaO ₄ as a main component, a powder obtained by mixing a powder having a molar ratio of Li ₂ CO ₃ : Ta ₂ O ₅ = 7: 3 and firing at 1300 ° C. for 12 hours was used. ..

Then, set the small container into an electric furnace, the furnace as a N ₂ atmosphere and heated at 750 ° C. 20 hours. Subsequently, an electric field of 4000 V / m was applied in the approximate + Z-axis direction of the LT substrate between 750 ° C. and 500 ° C. in the temperature lowering process, and then the temperature was gradually lowered to room temperature.

After this treatment, the surface of the piezoelectric layer was polished by about 10 nm to complete a composite substrate composed of the LT piezoelectric layer and the Si support substrate. No cracks or cracks occurred on this composite substrate. Moreover, when the maximum height Rz of the surface roughness was measured using an atomic force microscope (AFM), the value was 1 nm.

As in Example 1, the composite substrate thus produced was observed to be induced by applying vertical vibration in the thickness direction to the main surface and the back surface. As a result, piezoelectricity was observed at all points of the bonded substrate. The response could be observed and the piezoelectricity could be confirmed.

Further, as a result of performing laser Raman spectroscopic measurement on several points on the surface of the piezoelectric layer and calculating the amount of Li in the same manner as in Example 1, the amount of Li was 50.2 mol% in all the measurement points and was uniform. It was a pseudo-stoikiometry composition.

Further, with respect to the composite substrate of Example 4, electrodes were formed in the same manner as in Example 1, a resonator was produced, and the SAW resonator was evaluated in the same manner as in Example 1. The results are shown in Table 1 below. Shown.

<Example 5>
In Example 5, first, a 42 ° rotating Y-cut having a thickness of 300 μm was obtained from a 4-inch diameter lithium tantalate (Li: Ta = 48.3: 51.7) single crystal ingot having a congluent composition subjected to a single polarization treatment. The lithium tantalate substrate was cut out. Next, the surface roughness of the cut out LT substrate was adjusted to 0.15 μm in arithmetic average roughness Ra value by the wrapping step, and the thickness of the LT substrate was set to 250 μm.

Further, both sides of the LT substrate were polished to obtain a quasi-mirror surface having a surface roughness of 0.01 μm in Ra value. Subsequently, this LT substrate was embedded in a powder containing Li ₃ TaO ₄ as a main component, which was spread in a small container. At this time, as the powder containing Li ₃ TaO ₄ as a main component, a powder obtained by mixing a powder having a molar ratio of Li ₂ CO ₃ : Ta ₂ O ₅ = 7: 3 and firing at 1300 ° C. for 12 hours was used. ..

Then, set the small container into an electric furnace, the furnace as a N ₂ atmosphere and heated at 990 ° C. 50 hours to diffuse Li to LT substrate. After this treatment, one side of the LT substrate was mirror-polished.

Then, with respect to the LT substrate subjected to the Li diffusion treatment, the half width (FWHM1) of the Raman shift peak near 600 cm ^-1 was measured from the surface to the depth direction using the same laser Raman spectroscopic measuring device as in Example 1. When the Li amount was calculated from the measured half-value width using the above equation 1, the profile of the Li amount in the depth direction shown in FIG. 5 was obtained.

Next, as a support substrate, a sapphire substrate having a thickness of 500 μm and a mirror surface on one side was prepared. Then, it was confirmed that the surface roughness of the mirror surface of the LT substrate and the sapphire substrate subjected to the Li diffusion treatment was 1.0 nm or less in RMS value.

Subsequently, hydrogen molecule ions were injected from the mirror surface side of the LT substrate. At this time, the dose amount was 9 × 10 ¹⁶ atm / cm ² , and the accelerating voltage was 160 KeV. At this time, the position where the ions are injected is a position at a depth of 900 nm from the surface, and the amount of Li at that position is 50.1 mol%.

Next, the LT substrate and the sapphire substrate that had been ion-implanted were bonded using the surface-activated room temperature bonding method in the same manner as in Example 1. Further, in the same manner as in Example 1, the LT substrate was separated in the ion implantation section, and the surface of the piezoelectric layer was polished to obtain a bonded substrate composed of the LT piezoelectric layer and the sapphire support substrate.

The thickness of the piezoelectric layer at this time was 900 nm, but the surface of the piezoelectric layer was polished by 200 nm to make the thickness of the piezoelectric layer 700 nm. Moreover, when the maximum height Rz of the surface roughness was measured using an atomic force microscope (AFM), the value was 1 nm. No cracks or cracks occurred on this composite substrate.

As in Example 1, the composite substrate thus produced was observed to be induced by applying vertical vibration in the thickness direction to the main surface and the back surface. As a result, piezoelectricity was observed at all points of the bonded substrate. The response could be observed and the piezoelectricity could be confirmed.

Further, as a result of performing laser Raman spectroscopic measurement at several points on the surface of the piezoelectric layer and calculating the amount of Li in the same manner as in Example 1, the amount of Li was 50.0 mol% at all the measurement points and was uniform. It was a pseudo-stoikiometry composition.
In this LT substrate, the amount of Li is reduced by a maximum of 0.1 mol% by ion implantation.

Further, with respect to the composite substrate of Example 5, electrodes were formed in the same manner as in Example 1, a resonator was produced, and the SAW resonator was evaluated in the same manner as in Example 1. Almost the same result was obtained.

<Example 6>
In Example 6, first, a 42 ° rotating Y-cut having a thickness of 300 μm was obtained from a 4-inch diameter lithium tantalate (Li: Ta = 48.3: 51.7) single crystal ingot having a congluent composition subjected to a single polarization treatment. The lithium tantalate substrate was cut out. Next, the surface roughness of the cut out LT substrate was adjusted to 0.15 μm in arithmetic average roughness Ra value by the wrapping step, and the thickness of the LT substrate was set to 250 μm.

Further, both sides of the LT substrate were polished to obtain a quasi-mirror surface having a surface roughness of 0.01 μm in Ra value. Subsequently, this LT substrate was embedded in a powder containing Li ₃ TaO ₄ as a main component, which was spread in a small container. At this time, as the powder containing Li ₃ TaO ₄ as a main component, a powder obtained by mixing a powder having a molar ratio of Li ₂ CO ₃ : Ta ₂ O ₅ = 7: 3 and firing at 1300 ° C. for 12 hours was used. ..

Then, set the small container into an electric furnace, the furnace as a N ₂ atmosphere and heated at 990 ° C. 50 hours to diffuse Li to LT substrate.

Then, with respect to the LT substrate subjected to the Li diffusion treatment, the half width (FWHM1) of the Raman shift peak near 600 cm ^-1 was measured from the surface to the depth direction using the same laser Raman spectroscopic measuring device as in Example 1. When the Li amount was calculated from the measured half-value width using the above formula 1, a profile in the depth direction of the Li amount almost the same as in Example 5 shown in FIG. 5 was obtained.

Subsequently, hydrogen molecule ions were injected from the mirror surface side of the LT substrate. At this time, the dose amount was 9 × 10 ¹⁶ atm / cm ² , and the accelerating voltage was 160 KeV. At this time, the position where the ions are injected is a position at a depth of 900 nm from the surface, and the amount of Li at that position is 50.1 mol%.

After depositing SiO ₂ by about 10 μm at 35 ° C. on the ion-implanted side surface of the LT substrate using a plasma CVD method, the surface on which the SiO ₂ was deposited was mirror-polished.

Next, as a support substrate, a Si (SiO ₂ / Si) substrate having a thickness of 500 μm and having a thermal oxide film on one side mirror surface was prepared. Then, it was confirmed that the surface roughness of the mirror surface of the SiO ₂ / LT substrate and the SiO ₂ / Si substrate was 1.0 nm or less in RMS value.

Next, the SiO ₂ / LT substrate and the SiO ₂ / Si substrate were bonded by using the surface-activated room temperature bonding method as in Example 1. Further, in the same manner as in Example 1, the LT substrate was separated in the ion implantation section, and the surface of the piezoelectric layer was polished to obtain a bonded substrate composed of the LT piezoelectric layer and the Si support substrate. In this bonded substrate, a SiO ₂ layer exists between the piezoelectric layer and the supporting substrate as an intervening layer.

The thickness of the piezoelectric layer at this time was 900 nm, but the surface of the piezoelectric layer was polished by 200 nm to make the thickness of the piezoelectric layer 700 nm. Moreover, when the maximum height Rz of the surface roughness was measured using an atomic force microscope (AFM), the value was 1 nm. No cracks or cracks occurred on this composite substrate.

As in Example 1, the composite substrate thus produced was observed to be induced by applying vertical vibration in the thickness direction to the main surface and the back surface. As a result, piezoelectricity was observed at all points of the bonded substrate. The response could be observed and the piezoelectricity could be confirmed.

Further, as a result of performing laser Raman spectroscopic measurement at several points on the surface of the piezoelectric layer and calculating the amount of Li in the same manner as in Example 1, the amount of Li was 50.0 mol% at all the measurement points and was uniform. It was a pseudo-stoikiometry composition.
In this LT substrate, the amount of Li is reduced by a maximum of 0.1 mol% by ion implantation.

Further, with respect to the composite substrate of Example 6, electrodes were formed in the same manner as in Example 1, a resonator was produced, and the SAW resonator was evaluated in the same manner as in Example 1. Almost the same result was obtained.

<Comparative example 3>
In Comparative Example 3, first, a lithium tantalate single crystal substrate (4 inch diameter, thickness 300 μm, 42 °) having a pseudo-stoikiometry composition (Li: Ta = 49.95: 50.05) subjected to a single polarization treatment was applied. Rotation Y cut) was prepared. This LT substrate is composed of a single crystal obtained by the double crucible method, and has a pseudo-stoikiometry composition as a whole. One side of this LT substrate was mirror-polished.

Next, as a support substrate, a sapphire substrate having a thickness of 500 μm and a mirror surface on one side was prepared. Then, it was confirmed that the surface roughness of the mirror surface of the LT substrate and the sapphire substrate subjected to the Li diffusion treatment was 1.0 nm or less in RMS value.

Subsequently, hydrogen molecule ions were injected from the mirror surface side of the LT substrate. At this time, the dose amount was 9 × 10 ¹⁶ atm / cm ² , and the accelerating voltage was 160 KeV. At this time, the position where the ions are injected is a position at a depth of 900 nm from the surface, and the amount of Li at that position is 49.95 mol%.

Next, the LT substrate and the sapphire substrate that had been ion-implanted were bonded using the surface-activated room temperature bonding method in the same manner as in Example 1. Further, in the same manner as in Example 1, the LT substrate was separated in the ion implantation section, and the surface of the piezoelectric layer was polished to obtain a bonded substrate composed of the LT piezoelectric layer and the sapphire support substrate.

The thickness of the piezoelectric layer at this time was 900 nm, but the surface of the piezoelectric layer was polished by 200 nm to make the thickness of the piezoelectric layer 700 nm. Moreover, when the maximum height Rz of the surface roughness was measured using an atomic force microscope (AFM), the value was 1 nm. No cracks or cracks occurred on this composite substrate.

As in Example 1, the composite substrate thus produced was observed to be induced by applying vertical vibration in the thickness direction to the main surface and the back surface. As a result, piezoelectricity was observed at all points of the bonded substrate. The response could be observed and the piezoelectricity could be confirmed.

Further, as a result of performing laser Raman spectroscopic measurement at several points on the surface of the piezoelectric layer and calculating the amount of Li in the same manner as in Example 1, the amount of Li was 49.8 mol% at all the measurement points and was uniform. It was a pseudo-stoikiometry composition.
In this LT substrate, the amount of Li is reduced by a maximum of 0.15 mol% by ion implantation.

Further, with respect to the composite substrate of Comparative Example 3, electrodes were formed in the same manner as in Example 1, a resonator was produced, and the SAW resonator was evaluated in the same manner as in Example 1. The result was slightly inferior to 5 and 6.

Claims (10)

A method for manufacturing a composite substrate including a piezoelectric layer and a support substrate, which comprises a step of injecting ions into the piezoelectric substrate, a step of joining the piezoelectric substrate and the support substrate, and a piezoelectric substrate. After the step of joining the support substrate, in the ion injection part of the piezoelectric substrate, the step of separating the piezoelectric layer bonded to the support substrate and the remaining piezoelectric substrate, and after the step of separating the piezoelectric material. A method for producing a composite substrate, which comprises a step of diffusing Li into a layer. A claim comprising a step of joining the piezoelectric substrate and the support substrate, followed by a step of raising the temperature of the piezoelectric substrate to the Curie temperature or higher and lowering the temperature to the Curie temperature or lower in a state where an electric field is applied. Item 2. The method for manufacturing a composite substrate according to Item 1. The production of the composite substrate according to claim 1 or 2, wherein after the step of joining the piezoelectric substrate and the support substrate, the step of raising the temperature of the piezoelectric substrate to restore the piezoelectricity is included. Method. The method for producing a composite substrate according to any one of claims 1 to 3, wherein in the step of diffusing Li into the piezoelectric layer, the piezoelectric layer has a pseudo-stoikiometry composition. The piezoelectric substrate, a composite substrate manufacturing method according to any of 請 Motomeko 1 of 4 you characterized as having a range of Li concentration is different over its thickness direction. The method for manufacturing a composite substrate according to any one of claims 1 to 5, wherein the piezoelectric substrate is lithium tantalate or lithium niobate. The method for manufacturing a composite substrate according to any one of claims 1 to 6, wherein an intervening layer is provided between the piezoelectric layer and the support substrate. The method for producing a composite substrate according to any one of claims 1 to 7, wherein the support substrate contains at least one material selected from silicon, sapphire, silicon carbide, and spinel. A step of bonding the pressure collector substrate and the supporting substrate, a composite substrate manufacturing method according to any one of 請 Motomeko 1 you characterized 8 of that performed by surface activation room temperature bonding method. The method according to any one of claims 1 to 9, wherein in the step of implanting ions into the piezoelectric substrate, the ion species is at least one ion selected from hydrogen ions, hydrogen molecule ions, and helium ions. Method of manufacturing composite substrate.

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